1. Field of the Invention
The present invention generally relates to an all-terrain vehicle, and particularly relates to an all-terrain four-wheeled vehicle provided with an automatic transmission type belt converter.
2. Description of the Related Art
In a case of an all-terrain four-wheeled vehicle which is provided with a gear transmission, but not provided with a belt converter (i.e. automatic V-belt transmission), the speed reduction ratio of the gear transmission is fixed. Therefore, when the gear transmission is shifted to a backward position by which the vehicle is moved backward, and when an engine speed of the vehicle is increased by operating a throttle of the engine, the speed of the vehicle is proportional to the engine speed. In other words, when a maximum power region of the engine is used, the increment of the vehicle speed is limited within a predetermined region set when the gear transmission has been shifted to the backward position.
On the other hand, in a case of an all-terrain four-wheeled vehicle which is provided with a belt converter and a gear type sub-transmission, when the gear transmission (gear type sub-transmission) of the vehicle is shifted to the backward position, the speed reduction ratio by the belt converter automatically changes in compliance with the engine speed and a load exerted upon the belt converter. In other words, the vehicle speed is changeable from a practical speed region to an unnecessary high speed region.
As the all-terrain four-wheeled vehicle which is provided with the belt converter, there has been proposed a vehicle which has a controller for controlling the engine speed so as to prevent the vehicle speed from reaching such an unnecessary high speed, when the vehicle moves backwards. For example, the controller includes an engine speed detector, a backward movement detector, an ignition limiter for cutting ignition of the engine when the engine speed reaches a predetermined value during the backward movement of the vehicle, and an ignition cut release switch which is of a manual button type, or of a manual lever type.
FIG. 11 is a flowchart showing steps for controlling the engine by the conventional controller. That is, at step S100, it is determined whether the position of the gear transmission (gear position) is a reversion position (i.e., position for the backward movement of the vehicle) or not. If YES, it proceeds to step S200 in which it is determined whether the ignition cut release switch is open or not. If YES, it proceeds to step S300 in which it is determined whether the engine speed is over and above a set value (predetermined value) or not. If YES, it proceeds to step S400 in which the ignition of the engine is cut so as to decrease the engine speed to a speed up to the set value.
Namely, when the engine speed becomes more than the predetermined value during backward movement of the vehicle, the ignition of the engine is cut so as to limit the engine speed to under the predetermined value. On the other hand, when the driver of the vehicle desires, the ignition cut of the engine can be released by operating (handling) the ignition cut release switch manually, in order to increase the engine speed.
Incidentally, as prior art relating to the present invention, Japanese Laid-Open Patent Publication No. 61-129473 discloses a straddle type all-terrain four-wheeled vehicle having no belt converter, in which when the engine speed is more than a predetermined value during backward movement of the vehicle, the engine speed is limited to a value under the predetermined value.
Concerning the all-terrain four-wheeled vehicle provided with the belt converter in which the engine speed is detected while the vehicle is running backwards and in which the engine speed is controlled to be smaller than the predetermined value, there are some problems as follows. That is,
(1) when a high load is exerted upon the belt converter during backward movement of the vehicle, a large power output (i.e. large drive power) is necessary. At this time, the driver must take the trouble to operate the ignition cut release switch manually inconveniently, in order to increase the engine speed,(2) it is necessary to arrange the ignition cut release switch near the driver, and there must be an arrangement of wiring which connects the ignition cut release switch to a controller, etc., thus creating additional cost, and(3) when the load exerted upon the belt converter frequently varies during backward movement of the vehicle, the operation of the ignition cut release switch is troublesome.